The present invention relates to a method of depositing layers of semi-insulating gallium arsenide, and particularly to a vapor phase epitaxy process of depositing oxygen doped gallium arsenide on a substrate.
Gallium arsenide has found considerable use in making certain types of electrical components, such as field effect transistors, transferred electron effect devices and the like. Certain types of these electrical components are formed in a layer of gallium arsenide of a desired conductivity type, generally N type, on an insulating substrate. The layer of gallium arsenide is generally epitaxially deposited on the insulating substrate. To obtain gallium arsenide layers of good crystalline quality, it is desirable to use a substrate which will nucleate the epitaxial growth of good crystalline quality material. Semi-insulating, i.e. high conductivity, gallium arsenide of good crystalline quality is most desirable for this purpose. However, high quality, semi-insulating gallium arsenide substrates are expensive. Therefore, it would be desirable to form a layer of high quality semi-insulating gallium arsenide on a substrate, which substrate could be of a poor quality and therefore less expensive. The semiconductor material for forming the semiconductor device can then be formed on the semi-insulating layer. Also, it would be desirable to be able to form the semi-insulating layer by the same basic technique as is used to form the semiconductor device material. This would permit the two materials to be formed in a sequence so as to reduce the cost of making the semiconductor device.